[jira] [Comment Edited] (SPARK-983) Support external sorting for RDD#sortByKey()

["Mark Hamstra (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SPARK-983?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14009875#comment-14009875 ] 

Mark Hamstra edited comment on SPARK-983 at 5/27/14 4:40 PM:
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I'm hoping these can be kept orthogonal, but I think that it is worth noting the existence of SPARK-1021 and the fact that sortByKey as it currently exists breaks Spark's "transformations of RDDs are lazy" contract.  I'm currently working on that issue, which is undoubtedly going to require at least some merge work to be compatible with the resolution of this issue.


was (Author: markhamstra):
I'm hoping these can be kept orthogonal, but I think that it is worth noting the existence of https://issues.apache.org/jira/browse/SPARK-1021 and the fact that sortByKey as it currently exists breaks Spark's "transformations of RDDs are lazy" contract.  I'm currently working on that issue, which is undoubtedly going to require at least some merge work to be compatible with the resolution of this issue.

> Support external sorting for RDD#sortByKey()
> --------------------------------------------
>
>                 Key: SPARK-983
>                 URL: https://issues.apache.org/jira/browse/SPARK-983
>             Project: Spark
>          Issue Type: New Feature
>    Affects Versions: 0.9.0
>            Reporter: Reynold Xin
>
> Currently, RDD#sortByKey() is implemented by a mapPartitions which creates a buffer to hold the entire partition, then sorts it. This will cause an OOM if an entire partition cannot fit in memory, which is especially problematic for skewed data. Rather than OOMing, the behavior should be similar to the [ExternalAppendOnlyMap|https://github.com/apache/spark/blob/master/core/src/main/scala/org/apache/spark/util/collection/ExternalAppendOnlyMap.scala], where we fallback to disk if we detect memory pressure.



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